The inflammatory response and the innate immune system serve to 1) recruit immune cells to the wound, 2) contain and kill invading organisms and 3) clear the wound of noxious substances. However, wound infections are commonplace after thermal injuries and represent a major cause of morbidity and mortality. Bacteria that colonize the wound grow as adherent, multicellular communities known as biofilms and the biofilm mode of growth renders the bacterial cells resistant to killing by antiseptics, antibiotics and host defenses, which may explain the nature of many wound infections. Recently we found that exogenously added ATP can stimulate bacteria adherence and biofilm formation on abiotic and biotic surfaces and in a burn wound and previous studies in the literature found that injured epithelial cells release large amount ATP into the extracellular space, which serves as a danger signal and activate host innate immunity. Therefore, the major objective of this project is to define the role of extracellular ATP in bacteria-host interactions within the thermal injury. We hypothesize that extracellular ATP severs as an inter-domain signal and modulate both bacteria and host responses in the burn wound and can be a target for managing wound infections. To test this hypothesis, we will use both in vitro and in vivo models to elucidate molecular mechanisms of extracellular ATP signaling in bacteria using Acinetobater baumannii and E. coli as model organisms focusing on biofilm development and examine the inflammatory cytokines and leukocyte bacterial killing within thermal injuries by modulating extracellular ATP using the enzyme apyrase. Success of this study will enhance a more comprehensive and basic understanding of bacteria-host interactions and bacterial pathogenesis and will likely lead to the development of novel approaches to prevent/reduce wound infections and other infectious diseases.